The "Center for the Study of Lung Disease at Yale" will implement a plan to achieve a major improvement of respiratory health among Americans during the five-year period of the proposed grant award. The philosophy on which it is based has the following premises: (1) To abolish the deleterious impact of lung disease upon the health of Americans we must know who is or becomes sick and and under what circumstances this happens. We must know the relative quantitative importance of different lung diseases in causing premature disability or early death; (2) Knowledge of disease prevalence should be used to set research priorities, so that we may learn more about diseases that affect or kill many Americans. Research on the description, early detection and pathogenesis of lung diseases is urgently required but needs to have clearly defined goals to meet its objectives of improving respiratory health. These goals should be based upon knowledge of relative disease prevalences; (3) Commonly used as well as new methods of treatment need to be evaluated carefully not only with respect to medical efficacy but also with respect to practical implementation and delivery and to their impact on the cost of health care and medical care; and (4) To prevent disabling lung disease we need better health care, better health care delivery, and other forms of social action. These will be most effective if they are based on a foundation of solid facts, well-understood inter-relations and thoroughly studied methods and techniques.